86 lines
3.4 KiB
GLSL
86 lines
3.4 KiB
GLSL
layout (location = 0) in vec2 a_pos;
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out vec2 v_uv;
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out vec2 v_world;
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out vec2 v_particle_velocity;
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out float v_particle_valid;
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layout (std140) uniform ParticleGpuValidationUBO {
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highp vec4 u_pass;
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highp vec4 u_marker;
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highp vec4 u_mask;
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highp vec4 u_visual;
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highp vec4 u_field_bounds;
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highp vec4 u_field_scale;
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highp mat4 u_matrix;
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};
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uniform sampler2D u_state_texture;
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uniform sampler2D u_previous;
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uniform sampler2D u_field_texture;
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uniform sampler2D u_next_field_texture;
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vec2 fieldUv(vec2 world) {
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return vec2((world.x - u_field_bounds.x) / (u_field_bounds.z - u_field_bounds.x),
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(world.y - u_field_bounds.y) / (u_field_bounds.w - u_field_bounds.y));
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}
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bool validFieldUv(vec2 uv) {
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return all(greaterThanEqual(uv, vec2(0.0))) && all(lessThanEqual(uv, vec2(1.0)));
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}
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void main() {
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v_uv = a_pos;
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v_world = a_pos;
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v_particle_velocity = vec2(0.0);
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v_particle_valid = 1.0;
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if (u_pass.x > 4.5) {
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gl_Position = u_matrix * vec4(a_pos * 8192.0, 0.0, 1.0);
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} else if (u_pass.x < 1.5) {
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gl_Position = vec4(a_pos * 2.0 - 1.0, 0.0, 1.0);
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} else if (u_pass.x > 3.5) {
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// a_pos.x packs State texel X plus one endpoint. The formal particle
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// path draws the StateRead -> StateWrite displacement in current map
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// clip space; it does not synthesize a fixed world-length streak.
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float endpoint = mod(a_pos.x, 2.0) * 2.0 - 1.0;
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vec2 stateIndex = vec2(floor(a_pos.x * 0.5), a_pos.y);
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vec2 stateUV = (stateIndex + vec2(0.5)) / u_mask.xy;
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vec4 previousState = texture(u_previous, stateUV);
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vec4 currentState = texture(u_state_texture, stateUV);
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vec2 currentPosition = currentState.rg;
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vec2 uv = fieldUv(currentPosition);
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vec4 field0 = texture(u_field_texture, uv);
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vec4 field1 = texture(u_next_field_texture, uv);
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vec2 velocity = mix((field0.rg * 2.0 - 1.0) * u_field_scale.x,
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(field1.rg * 2.0 - 1.0) * u_field_scale.y,
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u_marker.x);
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bool valid = validFieldUv(uv) && field0.a >= 0.5 && field1.a >= 0.5 && !any(isnan(velocity));
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vec2 mercatorVelocity = vec2(velocity.x, -velocity.y);
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float speed = length(mercatorVelocity);
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vec2 segmentPosition = endpoint < 0.0 ? previousState.rg : currentPosition;
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v_uv = stateUV;
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v_world = currentPosition;
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v_particle_velocity = mercatorVelocity;
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// A zero alpha is written by State on a respawn frame. This suppresses
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// oldPosition -> newRandomPosition cross-screen segments.
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v_particle_valid = valid && speed > 0.00001 && currentState.a > 0.5 &&
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distance(previousState.rg, currentPosition) > 0.000000001
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? 1.0
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: 0.0;
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if (v_particle_valid < 0.5) {
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gl_Position = vec4(-2.0, -2.0, 0.0, 1.0);
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} else {
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gl_Position = u_matrix * vec4(segmentPosition * 8192.0, 0.0, 1.0);
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}
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} else {
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if (u_mask.z > 0.5) {
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// Trail targets are viewport-sized screen-space history buffers.
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gl_Position = vec4(a_pos * 2.0 - 1.0, 0.0, 1.0);
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} else {
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// VALIDATION ONLY: a_pos is canonical z0 world geometry; u_matrix
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// is PaintParameters::matrixForTile() for the selected world copy.
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gl_Position = u_matrix * vec4(a_pos * 8192.0, 0.0, 1.0);
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}
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}
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}
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